Fix not_close_tag option

This should fix #25 The PR should preserve the original behavior of being with close tags by default. Without the option (default): ```lua M.not_close_tag = not (nil ~= false) M.not_close_tag = not (true) M.not_close_tag = false ``` With the option `true` ```lua M.not_close_tag = not (true ~= false) M.not_close_tag = not (true) M.not_close_tag = false ``` With the option `false` ```lua M.not_close_tag = not (false != false) M.not_close_tag = not (false) M.not_close_tag = true ```